Penglai Milky Cucumber (Apostichopus japonicus) is a new strain in Sea Cucumber ranching and aquaculture. In this paper, for a better understanding and identifying the similarities and differences between Penglai Milky Cucumber and Common Sea Cucumber, and for evaluating the potential use and increasing the natural populations of Penglai Milky Cucumber, the embryonic and larval development was observed under the light microscope, and the time course of embryonic and larval development was confirmed. At the water temperature of 19﹣21℃ and salinity of 31, the first meiosis and second meiosis completed at 12 minutes and 24 minutes respectively after insemination (Fig. 2c, d); the eggs developed to 2 cells at 1 hour, completed a cleavage every 30 minutes, developed to the blastula at 6 hours, and to the gastrula at 19 hours. The fertilized eggs grew into early auricularia at 40 hours after fertilization (Fig. 3a), and then into the mid-auricularia and auricularia at 5 days and 8 days, respectively. In addition, an irregularly shaped calcareous bone appeared at the end of posterior arm of the larva, and the water cavity was observed on the same side (Fig. 4a). The larvae underwent metamorphosis to become doliolaria at 10 days, when the irregular bone developed into gear bone and the second calcareous bone appeared. The larvae developed to pentactula at 12 days, and to juvenile Sea Cucumber at 14 days. There was no significant difference in the developmental time course between Penglai Milky Cucumber and Common Sea Cucumber (Table 1). Penglai Milky Cucumber was in pure white on the whole body after juvenile stage. However, the Common Sea Cucumber showed some pigment at surface in 45 days, especially at the bottom of parapodum (Fig. 5b), and more than half of the juveniles were full of pigment at 60 days. In conclusion, Penglai Milky Cucumber is different from Common Sea Cucumber (Selenka) as indicated by its white body, which makes it attractive to. aquaculture companies and institutions, and the data of this study will provide reliable theoretical basis for Penglai Milky Cucumber′s research in the future.